Apparatus for electrical carbonization of coal



Sept 28, 593?. R. a, STITZER 2,094,027

APPARATUS FOR ELECTRICAL CARBONIZATION 0F COAL Original Filed Aug. 14,1935 2 Sheets-Sheet l COAL RETORT :LEci'Rom: SCRUBBER 3 AIR CONDENSER Icouoznssn 4m? FUEL GAS q i TRANSFORMER gown NSATE c c mosnsxrs i com: 51AM FIG. I

5040/7 B. Sfifzer INV/ENTOR YMEM ATTORNEY Patented Sept. 28, 1937 UNITEDSTATES PATENT OFFICE APPARATUS FOR ELECTRICAL CARBONIZA- TION F COALRalph B. Stitzer, Sheifield, Ala.

Original application August 14, 1935, Serial No.

Divided and this application December 4,1935, Serial No. 52,852

2 Claims.

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) terials, particularly thecarbonization'of bituf.

minous coal to form a coke suitable for domestic and industrial uses.

This application is a division of my original application, Ser. No.36,165, filed August 14, 1935.

One of the objects of this invention is to pro- 5 vide a continuous andefiicient apparatus for the carbonization of solidcarbonizable materialsin which electrical current is used as the source of the heat requiredfor the operation. Another object of this invention is to eliminate thedifliculties encountered in the carbonization of those coals whichbecome plastic prior to carbonization.

' Other objects of this invention include the provision for a means ofwithdrawal of the volatile carbonization products, which is aparticularly se-v rious problem when highly coking coals are carbonized.

It has been proposed that solid carbonizable materials be heated by aflexible electrical heating element located in the central portion of acolumn or coal with the lower end of the element connected with amechanical device for reducing the coke residue into fragmentssufliciently reduced to facilitate removal from the retort. It

has been proposed also to heat a charge centrally with an'electrlcalresistor and continue-the passage of current through the coke formedaround the resistor until the entire charge is carbonized,

followed by the removal of the coke, thereby presenting a discontinuousoperation. These and 40 other processes, of which the above examplesare,

illustrative, have certain disadvantages, each of which may include oneor more of the following: First, the process is discontinuous; second,coking coals adhere to theheating elements during the 45. time in whichthey are plastic and the carbonized I residue prevents rapid heattransfer from the element to the coal mass; third, the plasticizing 55 Ihave discovered a continuous process for the electrical carbonization,of solid carbonizable material, by electrically heating a column ofsolid carbonizable material surrounded by an envelope of carbonizedmaterial; by passing a supply of inert gas downwardly through the innerzone of 5 .the charge to keep the uncarbonized charge in the inner zonesubstantiallyfree from volatile condensable carbonization products, bywithdrawing the inert gas with the volatile carbonization productsupwardly through the outer zone of the carboni'zed portion of the chargewhich is separated from the inner zone by a gas'impervious partition .inthe upper portion of the retort; by separating tar and other condensablematerials from the. j gases so withdrawn to form a fuel gas which may beused as a source of the inert gas admitted "to the top of the column ofthe coal charge and. by passing a portion of the fuel gas or other inertgas upwardly from the bottom of the retort to cool the coke below thezone of electrical heating and to heat the ,coal and coke above thatzone. 5

In the accompanying drawings, which form a part of the specification,and wherein reference symbols refer to like parts whenever they occur,

Fig. 1 is a diagrammatic, vertical, sectional view of one form ofapparatus for the embodi: ment of my process;

Fig. 2 is a vertical, sectionalview of the elec trical carbonizationretort,

Fig. 3 is a horizontal sectional view taken at the sectional line A--Ain Fig. 2,

Fig. 4 is a horizontal sectional View taken at the sectional line B--Bin Fig. 2,

Fig. 5 is a horizontal sectional view taken at the sectional line' (3-0in Fig. 2, and

Fig. 6 is a horizontal sectional view taken at the sectional line D -Din Fig. 2. 1

In Fig. 1, coke is charged into the outer zone in the top of thevertical carbonization retort l, 40 which is between the inner wall ofthe retort and the gas impervious partition 2. Coal is charged into theinner zone in the top of retort I, which is surrounded by partition 2.The charge of coal surrounded bythe' envelope of coke moves downwardlythrough the retort between a pair of electrodes or a plurality ofelectrodes, located 'in and flush with the opposite faces of the wallof, the retort I, and represented 'by electrodes 3. The

coal in the charge between theelectrodes 3, is carbonized largelyfromthe heatproduced by the. passage of an, electrical current through thecarbon portion of the chargesurrounding the coal portion of the charge,which serves as a resistor between electrodes 3', the current to theelectrodes being supplied from the electrical service lines 4, throughthe transformer 5. The hot coke which has passed downwardly pastelectrodes 3,

is cooled to a temperture below its ignition point in air by the upwardpassage of an inert gas, comprised of steam and some fuel gas, admittednear the bottom of the retort at a plurality of points represented byinlet 6. The cooled coke is withdrawn from the bottom of theretort bythe coke withdrawal means, l3. The inert gas admitted at inlet 6, isheated by contact with the hot coke below the zone of the electrodes 3,and with additional heat obtained in the zone between the electrodespasses upwardly to heat the charge in the zone immediately above theelectrodes. A further amount of an,- inert gas, comprised of fuel gas,is admitted through inlet 1, into the top of the inner zone in the topof the retort, into which the coal is charged and is passed downwardlyin a suificient volume to keep the uncarbonized coal in the inner zonesubstantially free from condensable carbonization products. The gaseousmixture consisting of the inert gas admitted at the bottom of theretort, the inert gas admitted at the top of the inner zone of theretort, and the volatile carbonization products, pass up wardly throughthe coke in the outer zone at the top of the retort and'are withdrawn atthe top of this outer zone. This gas from the retort, together withentrained solid and liquid particles, passes through the aircondenser 8,where the major portion of the tarry matter is removed, and through thecondenser 9, in which the major portion of the remaining volatilecondensable material in the retort gas is condensed by indirect coolingwith water and separated from the gas. The gas from theretort fromwhich'substantially all the condensable volatile matter has been removedpasses into the inlet of the blower I 0,

which serves tomaintain a substantially atmospheric pressure in the topof the outer zone of the retort I, and the gas delivered by blower I0 istreated in scrubbers II and I2 to remove valuable by-products, such asammonia and other nitrogen compounds, and otherwise prepare the gas fromthe retort for use as a fuel gas, such as by the removal of hydrogensulfide and other sulfur compounds. A portion of this fuel gas is usedas the supply for the inert gas admitted near the bottom of the retortI, through inlet 6, and into inlet 1, into the top of the inner zone ofthe retort.

In Fig. 2, the coke a, charged into the outer zone in the top of retortI, between the inner wall of the retort and partition 2, passesdownwardly and surrounds the charge of coal b, which is fed into the topof the inner zone surrounded by partition 2. The coke a, and the coal1), continue to pass downwardly into the zone between the electrodes 3,in substantially the same relative position which they occupied onpassing the bot-.

tom of partition 2. The coke a. serves as a res1stor when it comes incontact with the eleccarbonizes the coal 2), of the charge adjacent toit.

The coal so carbonized in turn serves as a reas it passes through thezone between the electrodes 3, is continually .until the coal 1), hasbeen carbonized in its entirety at the time, or shortly after it passesthe elevation of the bottom of the electrodes 3. The inert gas admittedpoint.

I table origin, suchas woods and nut shells. trodes 3, and the heatproduced by the passage of the electrical current through the coke 0,

through the inlet 6, passes upwardly and cools the hot carbonizedproduct in which the coke a, from the charge and the coke resulting fromthe carbonization of coal 1), is practically indistinguishable. Theinert gas so heated serves to as- 5 sist in the heating of the chargebetween the electrodes 3, and to preheat the charge in the zone abovethe elevation of the top of the electrodes.3. The inert gas admittedthrough the inlet I, in the top of the inner zone of the retort, passesdownwardly and keeps the uncarbonized coal b,in the inner zonesubstantially free from condensable carbonization products. The volatilecarbonization products and the inert gas admitted at the bottom of theretort, together with that admitted at the top of the inner zone of theretort, pass upwardly through the coke a, into the outer zone in the topof the retort and are withdrawn from the top of this zone as the retortgas.

In Fig. 3, which is a horizontal sectional view of a section near thetop of retort I, the coke portion of the charge a, in the outer zone isshown separated from the coal portion of thecharge b, in the inner zoneby partition 2.

In Fig. 4, which is a horizontal sectional View of a section of retortI, below the elevation of the bottom of the partition and above theelevation of the top of the electrodes, the coke portion of the chargea, is shown enveloping the coal portion 30 of the charge b.

In Fig. 5, which is a horizontal sectional iew of a section of theretort I, through the electrodes, a represents the coke portion of thecharge and the carbonized portion of the charge, the two beingpractically indistinguishable at this point,

surrounding the coal portion of charge b, whic the retort, a representsthe coke portion of the charge and the carbonized portion of the charge,the two being practically indistinguishable at this It is evident thatthere are numerous factors which will influence conditions for the mostsatisfactory operation of my invention, the actual. limits of whichcannot be established except by a detailed. study of each set of rawmaterials and 50 the intermediate and finished products involved. Theterm solid carbonizable material shall mean and include solidcarbonaceous material, which has not been subjected to a carbonizationprocess, and which may be heated to a sufficiently high superatmospherictemperature to remove the volatile products which it contains with theformation of a solid carbonized residue useful as a y domestic orindustrial fuel or otherwise in the arts. Examples of solid carbonaceousmaterial 60 include anthracite coal, non-coking and coking bituminouscoals, and materials of recent vege- The term carbonized material shallmean and int cludeany solid carbonaceous product resulting '65 from thecarbonization of a solid carbonizable material. Examples of carbonizedmaterial include low and high volatile cokes and charcoal. In theoperation of my process and apparatus it is preferred to use thecarbonized portion of the charge derived from substantially the samesource as the uncarbonized portion of the charge, ,1. e., it ispreferred to use a coke from bituminous coal in connection withthecarbonization of bituminous coal and his preferred to use a" hardwoodf5 charcoal derived from the same type of hardwood that is beingcarbonized, in. order that the respective resulting products may be ofuniform character.

The size of the carbonized portion of the charge preferably is such thatit will pass through a 1" mesh and be retained on a 0.25" mesh.Screenings which otherwise havev little value for metallurgical purposesmay. be used for this purpose. Should these screeiiings contain aconsiderable excess of very fine material, such as below a 0.25" mesh, asmall proportion of this material could be incorporated with thecarbonizable portion of the charge when this portion of the charge is acoking coal. The size of the solid carbonizable material preferably issuch that this portion of the charge will pass through a 2.5" meshscreen.

The ratio by weight of the carbonized material to the carbonizablematerial may vary within considerable limits, depending upon thematerials being processed. Using coke from bituminous coal and a cokingcoal of the sizes given above, the proportions may be varied from 10 to30% and 90 to 70% by weight, respectively.

The vertical retort shown in the respective drawings has a square crosssection but this cross section may be rectangular, hexagonal, octagonal,

' elliptical, round, or any other symmetrical cross section, so long asthe electrodes may be so placed in the opposite faces and flush with theinner faces of the .retort wall and operated in such a manner as toobtain complete carbonization of the carbonizable material which passesthroughthe zonebetween the electrodes.

'The partition in the topof the retort which forms the outer and innerzones in which the carbonized and carbonizable materials, respectively,are charged maybe concentric to the inner wall of a retort of uniformcross section from top to bottom or the cross section of the uppersection of the retort and the partition within may be circularregardless of the nature of the cross section of the zone above andbetween the electrodes. The partition forming the outer and inner zonesextends from the top of the retort to an elevation located above theelevation of the top of the electrodes, preferably to an elevationlocated above the top of the electrodes equal to the distance betweenthe electrodes, but may vary within a reasonable range, depending uponthe nature of the carbonizable material charged and the volume of inert,gas per unit weight of charge, passed downwardly through the charge inthe.inner zone.

The electrodes may be a pair,-or a plurality of electrodes, located inand flush with opposite faces of the retort. The power supplied to theelectrodes may be single phase or three phase alternating current ordirect current obtained from a standard-power circuit. ingcurrent isused, the transformer required is preferably a variable transformer inorder to permit flexibility in operation, due to such im- ,portantfactors as a change in the quality of r the charge and the chargingrate. I

The inert gas is admitted to the retort through a plurality of inletsnear or through the bottom of the retort at a suflicient rate to coolthe\ hot carbonized residue through which it passes countercurrently, toa temperature below the ignition point of th'e carbonaceous residue inair. This rate has been found to. be approximately to 13 cubic feet ofretort gas per pound of carbonizable material charged in carbon'izing a,coking coal at the rate of 400 to, 1000 pounds When 'alternatstantialproportion of material which is reactive at any stage in thecarbonization process,

and may include such materials as natural gas, producer gas, water gas,fuel gasproduced by this process, and steam. It is ordinarily preferredto use steam as the inert gas without or I with admixture of any of the.above mentioned gases. Steam alone may be used duringlow temperaturecarbonization of a carbonizable material, as well as during a hightemperature carbonization of a carbonizable material, in which thetemperature of the carbonaceous material reaches 1700 to 1900 F.,particularly when it is necessary to produce a gas of high calorificvalue. Under such conditions of high temperature carbonization, there issome dissociation of the water vapor but the operation of this processis so controlled as to prevent any substantial dissociation under theconditions for high temperature carbonization .used. Under thesesameconditions, the hydrocarbons in inert gas containing the same aredecomposed and result in the production of 'a gas of lower calorificvalue than that obtained using steam alone.

The inert gas is admitted into the top of the inner zone of the retortthrough one, or a plurality of inlets, at such a rate as to' keep theuncarbonized material in the inner zone substantially free fromcondensable products. This ratev has been found to be approximately oneto three cubic feet of inert gas per pound of carbonizable material incarbonizlng a coking coal at the rate of .400 to 1000 pounds per squarefoot of retort cross section between the electrodes per hour. The inertgas admitted into the top of the inner zone of the retort may be derivedfrom any source, so long as it is not substantially reactive at anystage of its contact with the carbonizable portion or carbonized portionof the charge, or so long as it does not contain any substantialproportion of material which is reactive at any stage of its contactwith the portions of the charge and may include such ma 1 this process.

The retortgas, which consists of the volatile carbonization products andthe inert gas admitted both at the bottom and at the top of the retort,is withdrawn from a plurality of the outlets ator'near the top of theouter zone in-the top of the retort and is cooled stepwise to reinovetarry matter andother condensablematerials by such means as one or aplurality of air-cooled condensers and one or a plurality of,watercooled indirect condensers. The gas so treated maybe used now as asource ofthe supply of the inert gas used in the processor this gas maybe scrubbed to remove valuable Icy-products,

such as ammonia and richer nitrogenous compounds, and otherwise preparethe gas from the retort for use as a fuel gas, such as by the removal ofhydrogen sulfide and other sulfur compounds. In either caseonly aportion of theard brick construction with a refractory lining.

The electrodes, preferably made of carbon block, are located in oppositefaces and flush with the inner faces of the retort in a mid-section ofthe retort. Substantially gas-tight-charging mechanisms, fitted intoagas-tight metal retort top, supply the carbonized material and thecarbonizing material from their respective hoppers into the inner andouter zones, respectively, in the top of the retort.

I have found it possible to charge carbonizable material at amuch'higher rate by using my process and apparatus as herein describedthan has been possible heretofore. Coking coal ischarged and carbonizedat a rate of more than 400 pounds per square foot of retort crosssection between the electrodes per hour, as compared with a rate of lessthan 100 pounds per square foot of retort' section per hour, usinganother process and apparatus. I have found also that it ispossibletoaccomplish the carbonization using my process and apparatus hereindescribed by the use of a considerably smaller quantity of electricalenergy.

For instance, in the ,carbonization of a coking coal at the rate of- 450pounds per square foot of retort cross section between the electrodesper hour, 310 kw. hr. per ton of coal charged were required as comparedto the other process and apparatus referred to above at the rate of 88pounds of coking coal per square foot of retort cross section per hour,350 kw. hr. per ton of coal were required.

It will be seen, therefore, that this invention actually may be carriedout by the modification of certain details without departing from itsspirit or scope.

I claim: i. In an apparatus for the electrical carbonizatlon of coal ina vertical retort bypassing a column of charge, which comprises cokingcoal surrounded by an envelope of coke, between electrodes located incontact with and on opposite sides of the charge, the combination of avertical retort; a gas impervious partition extending from the top ofthe retort to an elevation above the elevation of the top of theelectrodes located in v .the face ofopposite walls of the retort fromone half to the full distance between the electrodes, to form an innerzone and an outerzonein the top of the retort; a means for admittinginert gas into the top of the inner zone, into which coal is charged, tokeep the uncarbonized coal substantially free from volatilecarbonization products;' a means for admitting inert gas to a zone inthe retort below the elevation of the bottom of the electrodes and ameans for withdrawing a gaseous mixture, which-comprises the inert gasadmitted into the top of the inner zone, inert gas admitted to the zonebelow the electrodes and V the volatile carbonization products, from thetop of the outer zone, into which coke is charged.

2. In anapparatus for the electrical carbonization of solid carbonaceousmaterial in a vertical retort by passing a column of charge, whichcomprises solid carbonaceous material surrounded by an envelope ofcarbonized carbonaceous material, between electrodes located in contactwith and on opposite sides of the charge, the combination of a verticalretort; a gas impervious partition extending from tlie top of the retortto of the retort from one half to the full distance an elevation abovethe elevation of the top of the electrodes located in the face ofopposite walls *between the electrodes, to form an inner zone-

